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Flood risk increases with March snowfall

FARGO – Early March snowfall slightly increased the risk of major flooding on the Red River, and a Fargo official said the city isn’t taking the spring flood outlook lightly.

In its latest outlook released Thursday, the National Weather Service pegged the Red’s chances of topping the 30-foot major flood stage in Fargo-Moorhead at 88 percent, up from 79 percent in the last flood outlook Feb. 21.

Thursday’s outlook gives the river a 5 percent chance of exceeding 38.2 feet, up from a 5 percent chance at 37.8 feet in the last outlook.

Flood risks increased another 5 percent to 10 percent in most areas since the Feb. 21 outlook, the weather service said.

Officials say Fargo is well-protected to 38 feet without sandbagging. The city’s record flood crest is 40.84 feet on March 28, 2009.

City Commissioner Mike Williams said the city is “very comfortable” at a river level of 30 feet, and raising the protection level to 40 feet in preparation for a 38-foot crest would require only 100,000 sandbags, compared with the 800,000 that were needed in 2009 on South River Drive alone.

The city has 750,000 sandbags left over from 2011 if needed, he noted.

Officials are taking inventory and ordering pumps in case a big spring rain overwhelms lift stations while the river is flooding, Williams said.

“We don’t ever take it lightly,” he said. “We plan for the worst and hope for the best.”

A March 4 snowstorm added almost an inch of water to the snowpack, bringing the snow-water equivalent up to at least 3 inches across the Red River Basin, the weather service said. The far northern basin’s snowpack is pushing 5 inches of snow-water, and the southern basin is holding 4 to 5 inches, with higher amounts in isolated areas – “much above normal” for both areas, the outlook stated.

The Red River now has a 75 percent chance of exceeding major flood stage at Wahpeton and a 53 percent chance at Pembina. The Wild Rice River at Abercrombie has a 58 percent chance of major flooding, the outlook stated.

While the flood risk didn’t change much for the southern Red River Valley, heavy snowfall in the northern valley will send more water into the north-flowing river and slow its progress, which will affect flooding in the south, said Jeff Makowski, meteorologist at the weather service office in Grand Forks.

The heavy snowpack has lessened springtime drought conditions, and some snowmelt will infiltrate the topsoil and deeper layers. But most of the excessive snowpack is expected to contribute to runoff and flood potential, the weather service said.

Below-normal temperatures and above-normal precipitation are expected into late March, the weather service said.

A weather system moving through the area tonight through Saturday night could drop 3 to 5 inches of snow south of a line from Lidgerwood to Bemidji, Minn., the weather service said. Snow amounts should be less than an inch elsewhere in the Red River Valley. Freezing rain or sleet also is possible in southeastern North Dakota and west-central Minnesota.

The forecast calls for highs of 32 degrees today, 33 degrees Saturday and in the mid-20s to 30 through Wednesday, which will cause minor melting, Makowski said.

“But in terms of the faster melting with the really warmer temperatures, that doesn’t look too likely over the next week to week and a half at least,” he said. “And then it’s really dependent on exactly what the jet stream looks like and where we get these storm systems to pass through.”